Bow returned to poor tiller

[Black Moshannon]

I’m working on a 66” by 1 1/4-1 1/8 hickory D bow. After tillering it to 60# at 26”  I heat treated it, a good dark deep one. One limb originally had more reflex, the other limb had a deflexed spot. During the heat treating i reflexed the whole bow some, more than I meant to actually. When it was done and I strung it yesterday I was dismayed to see it had returned to its terrible tiller which it had when I first strung it before heat treating! It seemed like I lost a lot of the work I did before heat treating. At this point I have it working back in to a decent looking tiller but I’m barely going to make the target weight.

[PatM]

Your post isn't really clear.  How did the bow compare at original brace to it's strung profile?  Did you ever get good looking tiller at brace and draw before heat treating?

 

[sleek]

So long as each limb bends the same amount and the bend is evenly distributed throughout the limb, the tiller is good, noth limbs dont need to look the same.

[Black Moshannon]

It was at a good tiller profile before the heat treat..when first, very first braced, the tiller was pretty bad.

[Black Moshannon]

So long as each limb bends the same amount and the bend is evenly distributed throughout the limb, the tiller is good, noth limbs dont need to look the same.

Ok, I think the problem has been solved again, the tiller looks ok and it’s at 60#at full draw. The deflexed limb was fooling my eye.

[Black Moshannon]

One thing I can say for sure, is both limbs were bending evenly before the heat treat, and afterwards they were not anymore

[bownarra]

The 2nd time you heated it you undid the corrections you did on the first heat treat.
Once you have corrected/bent a piece of wood with heat if that same piece experiences the smae or higher heat again without being clamped in possition the corrections you intially made will reverse.
Try bending a recurve, letting it cool and 'set' in plce. Then point the heatgun at it and watch it uncurl again.

[Marc St Louis]

One thing I can say for sure, is both limbs were bending evenly before the heat treat, and afterwards they were not anymore

That is to be expected, why I heat-treat well before tillering to full draw

[Black Moshannon]

The 2nd time you heated it you undid the corrections you did on the first heat treat.
Once you have corrected/bent a piece of wood with heat if that same piece experiences the smae or higher heat again without being clamped in possition the corrections you intially made will reverse.
Try bending a recurve, letting it cool and 'set' in plce. Then point the heatgun at it and watch it uncurl again.

I only heat treated this one once. I’ve noticed what you’re saying with other bows.

One thing I can say for sure, is both limbs were bending evenly before the heat treat, and afterwards they were not anymore

That is to be expected, why I heat-treat well before tillering to full draw

Well at least it wasn’t an outlandish phenomenon then. I meant to heat treat at 20 inches of draw or so but of course I took off too much wood and continued tillering right up to full draw...

[JohnL]

 +1 on what Marc said.
 
     It's also worth mentioning, that I have never had a finished hickory bow hold the work I've done, when trying to flatten kinks of deflex, while doing a heat-treat.  I'm always so proud, after I take it off the form, of how I've flattened-out the deflex, but they always come back, as soon as the bow is braced.  I even take it past flat, to make-up for the spring-back; but with hickory, you're more likely to end up with tension cracks on the belly in that spot, than you are with a fix for the deflex.
Same applies for trying to "undo" set, with a back-set heat-treat.  You can fix Osage with those methods, but not hickory.
 *That's been my personal experience, anyway.

-John

[Black Moshannon]

+1 on what Marc said.
 
     It's also worth mentioning, that I have never had a finished hickory bow hold the work I've done, when trying to flatten kinks of deflex, while doing a heat-treat.  I'm always so proud, after I take it off the form, of how I've flattened-out the deflex, but they always come back, as soon as the bow is braced.  I even take it past flat, to make-up for the spring-back; but with hickory, you're more likely to end up with tension cracks on the belly in that spot, than you are with a fix for the deflex.
Same applies for trying to "undo" set, with a back-set heat-treat.  You can fix Osage with those methods, but not hickory.
 *That's been my personal experience, anyway.

-John

It’s good to hear someone else struggling with hickory. I like it but it does seem to hold its own shape like a fiend. My last one I steamed, dry heated, and even bent it after the heat treat, attempting to remove kinks and lateral warp, all to have it go back. That bow did end up with some chrysals on the belly. So far after a good many shots the bow is still fast and has low string follow so maybe I didn’t do too much harm. My new plan with hickory is to immediately after cutting, reduce the stave to almost finished dimensions and strap it onto a form to dry.

[Azmdted]

One thing I can say for sure, is both limbs were bending evenly before the heat treat, and afterwards they were not anymore

It’s also possible that each limb got a slightly different heat treatment which caused one to pull out more than the other.   I saw this on a hickory I did as I tillered it after heating.  My last couple hickory bows I’ve used the fire hardening approach and I rotate the caul every 10-15 minutes to ensure that it’s heating each limb evenly. It’s working great so far.

[PatM]

It seems odd that Hickory wants to return to original shape and yet it's notorious for following the string.

[Black Moshannon]

It’s possible I cooked the limbs unevenly.

I’ve noticed elm seems to take corrections and hold them pretty well. I don’t know why hickory doesn’t. I think the string follow with hickory has to do with it soaking in moisture like a fiend, I guarded against this zealously on this bow and oh my, it really has low string follow, right now it has none at all. Most of my bows end up with 1.5 inch average string follow. I’m not a maker of high performance bows.